This protocol enables
WebView policy delegates to communicate with listener objects. A listener object conforming to this protocol is passed as one of the arguments to web view policy delegate methods.
- macOS 10.10+
This protocol allows delegates to handle download decisions asynchronously. For example, the policy delegate may display a sheet, and the listener object gets notified only after the user clicks an OK or Cancel button. You do not directly create objects that conform to this protocol.